so probably a dumb question but are the cooling fan running the noise you hear after you shut it down? I've not seen the tune from these trucks, but first time I drove my c6 hard in the mountains, pulled over at the over look and shut it off without thinking about it being hot the fans came on. turns out in the e38 ecm (which I believe was used in some of these trucks) if you meet a certain parameters it will run the cooling fan after turning the car off. help cover the heat soak hit.